1. Field of the Invention
This invention relates to dynamic pushing and pulling capacity testing devices, specifically to such manually-propelled vehicles which are used to assess consistency of effort during a pushing and pulling assessment and to such manually-propelled vehicles that are used to exercise a muscle. Various equipment and methodologies are currently used to evaluate validity of effort in subjects who have filed insurance claims for physical injury. In a therapeutic setting, various devices and methods are used to rehabilitate a muscle.
2. Description of the Prior Art
Work-related injuries represent a major source of financial loss each year for businesses and injured parties in this country. Significant claims for personal injury also arise from motor vehicle accidents and other accidents which are unrelated to the workplace. Together, the medical and indemnity expenses associated with these claims cost billions of dollars annually.
A disproportionate amount of money in compensable cases is spent on a relatively small number of the claims which are filed. In part, this occurs because some claimants may need to undergo surgery and/or extensive physical rehabilitation. In other cases, expenses related to treatment, rehabilitation and indemnity are inflated because individuals abuse a compensation system and receive treatment or monetary awards that are not justified.
Various physical tests are often performed on compensation claimants in order to determine the need for treatment, the necessity of return to work restrictions or to arrive at a financial settlement for a case. In such tests, it is essential that measures be incorporated in a test protocol to objectively identify performances that are not reflective of maximum efforts.
Not infrequently during an assessment of an individual's functional abilities, apparent inconsistencies in performance are noted. The classic example of such inconsistent behaviors may occur during a hand grip assessment in which a low back pain patient demonstrates physical weakness and wide variability between trials on a hand-held dynamometer. (Hand grip weakness can not be explained in the physical context of a low back injury.) Some individuals in a testing or therapeutic environment, then, appear to magnify the extent of the pain and disability as a result of non-physical factors. Behavioral, monetary, psychological and social factors forces are thought to also affect assessment of functional abilities, particularly in compensable cases. Mechanic and Matheson have written extensively about this phenomenon, known in the field as "symptom magnification."
As a result of abuses of compensation systems by defendants and petitioners alike, there is a demand for comprehensive functional assessment of claimants. Such evaluations can be used to assess validity of effort and to manage decisions regarding indemnity, treatment, an individual's ability to return to work. In compensation cases, it is necessary to objectively determine if a physical performance reflects a maximum physical effort. Performances that are not highly reproducible can not logically be classified as valid expressions of maximum physical capacity. Therefore, it has become beneficial to develop tools and methods which help clinicians objectively assess functional abilities, particularly lifting, carrying, pushing and pulling, because these are the most commonly performed material handling tasks.
Susan Isernhagen proposes the "kinesiophysical" approach to functional assessment. A standard protocol is administered to test subjects. Using this method of evaluation, therapists are reportedly able to identify valid efforts by noting the presence or absence of biomechanical failure during assessments of lifting, carrying, pushing and pulling capacities. Isernhagen proposes specific criteria which are said to indicate biomechanical breakdown and a valid effort. The application of the criteria, however, relies on the accuracy of the therapist's assessment of the physical performance, as opposed to extensive analysis of numerical data gathered during the test.
In the kinesiophysical protocol, termination points for various material handling tasks are determined by the therapist. Inter-tester variability in interpretation of performance is inevitable with such an approach. A subjective approach has the potential to expose a test subject to injury if a therapist misjudges physical capacity or effort. There is also the potential to incorrectly classify consistency of effort. The evaluation of symptom magnification does not play an important role in the approach advocated by Isernhagen.
Matheson and Blankenship propose the "psychophysical" method of functional assessment. These clinicians propose that any physical performance is affected by psychological as well as physical factors. The psychophysical approach is the most common type of protocol used to evaluate claimants in a compensation system.
Material handling activities in a psychophysical protocol are terminated when a test subject indicates an inability to safely perform at a higher workload or when, in the clinician's opinion, the safe biomechanical limits of the subject have been attained. Both of these termination points are subjective. In contradistinction to the kinesiophysical method, the method advocated by Matheson and Blankenship places a more emphasis on interpretation of raw data in order to add some objectivity to the assessment of validity of effort. Furthermore, Matheson and Blankenship place a greater value on incorporating cross-reference tests and observations into a protocol. Psychological and behavioral factors are also given more weight. For example, Waddell testing for non-physical pain responses in low back pain patients are routinely administered. (In landmark research, Gordon Waddell found a correlation between reports of pain arising from purposely-benign physical maneuvers and high scores on the scales for hypochondriasis, hysteria and depression on the Minnesota Multiphasic Personality Inventory.) Pain questionnaires intended to identify possible symptom magnification are also typically filled out by subjects in the psychophysical model.
Matheson and Blankenship also advocate the use of various multiple-trial isometric tests to assess consistency of effort. Inter-test variability between trials is analyzed with the coefficient of variation. It is noted, though, that the research on the coefficient of variation is divided as to the usefulness of this statistic in correctly classifying effort during isometric strength testing.
"Distraction testing" has become and acceptable method of assessing consistency of effort Waddell formally proposed the concept in the research previously cited. He insisted that for such testing to be valid, it must be "non-emotional, non-hurtful and non-surprising." Clinicians using the psychophysical method of evaluation frequently develop their own distraction tests for use during functional assessment, varying the protocols proposed by Matheson and Blankenship in accordance with their professional experience and judgement.
Basic testing equipment for assessing dynamic pushing and pulling capacities may involve the use of a cart upon which weight is place. There are four primary disadvantages to this approach. First, the amount of weight needed to create a high workload would involve placing large quantities of weight onto the cart. This is expensive, labor intensive and may even expose the clinician to injury. Second, the weight placed on the cart may be seen by the test subject and, therefore, has the potential to affect performance. Third, it is difficult to use a multiple trial test protocol to assess consistency of effort because of the visual cues available to the test subject. Fourth, incremental changes in workload can be effected, but may require removing or adding relatively large amounts of weight from the cart.
American Therapeutics, Macon, Georgia, markets "The Sled," which is an apparatus consisting of a platform mounted on two runners. Handles attached to the platform are grasped by the test subject. By generating a pushing or pulling force, the device can be maneuvered across a surface. The workload can be adjusted by adding weight to the platform. A force gauge is then connected to the invention and pushed or pulled by the clinician to determine the amount of pushing and pulling forces demonstrated by the test subject. Conducting multiple trials to assess consistency of effort is not practical with this device because the workload can bee seen by the subject. Small, incremental adjustment of the workload is difficult to accomplish. Test subjects may be reluctant to exert force against an object which has no wheels and, as a result, test results can be skewed. Furthermore, the condition of the floor (for example, the presence or absence of dust or the variability in the finish of a concrete floor) may affect the amount of force necessary to push the device from one location in the room to another. Lastly, this device is unsuitable for use on a hardwood floor because the runners of the sled can damage the surface over which it is maneuvered.
There are variety of testing devices capable of measuring isometric pushing and pulling capacities. Examples of such inventions are U.S. Pat. Nos. 4,972,711 and 5,275,045. This mode of testing maintains the test subject in a static body posture while the subject exerts force against a stationary object. However, there are few work-related activities which require the production of force which is exerted against an immovable object. Also, that is no direct relationship between isometric and dynamic physical abilities. Clinical research, as already noted, is divided on the usefulness of the coefficient of variation in assessing consistency of effort. With regard to its use as a rehabilitation mode, the benefits of isometric exercise are specific to the range of motion in which it is performed. Typically, this type of exercise is capable of increasing strength in a only narrow range of motion (approximately 10-15 degrees).
Numerous isokinetic devices have been invented. Such inventions are described in U.S. Pat. Nos. 3,465,592 and 4,907,797. U.S. Pat. No. 4,890,495 was specifically intended to measure isokinetic pushing and pulling abilities. Some isokinetic devices have the capability to measure pushing abilities while others test and measure only isolated joints and groups of muscles. These inventions apply an accommodating resistance to the test subject's efforts and, through mechanical and/or electronic means, the workload is maintained at a constant velocity. An isokinetic workload is a machine-generated, artificial workload significantly unlike the isoinertial workloads found in the workplace. Thus, there is no direct relationship between isokinetic physical capacities and the physical demands in the actual workplace. Furthermore, no standardized approaches to assessing consistency of effort for performances on this type of equipment has been developed. Instead, clinicians administering such tests usually assess consistency of effort by visual inspection of graphs which depict a performance. The variability, as seen on a graph, is said to reflect differences between repetitions. However, the apparent differences between repetitions is, to a large degree, affected by the scale on which each axis of the graph is displayed. Thus, visual analysis of graphs results in inter-tester variability in interpretation. Finally, U.S. Pat. No. 4,890495 limits the distance the subject can maneuver the testing apparatus to less than ten feet, far less than is often required on the job.
U.S. Pat. Nos. 4,337,050 and 4,473,226 and 4,475,408 are incorporated into a device now commercially known as the BTE Work Simulator. This invention has a number of uses, including one feature which measures isoinertial pushing and pulling capacities. The advantage to using this equipment is that the workload is unseen and, therefore, the test subject can not use visual inspection to estimate a workload. Workloads on the device are controlled by the clinician. Resistance is generated by an electromagnet which applies a workload to a pulley. A rope is wound round the pulley and connected to a bar which is held by the test subject. The test subject exerts a pushing or pulling force against the hand-held bar, moving the bar and rope away from the device. The workload applied by this equipment is isoinertial, the same type of resistance that would be encountered in the workplace. The Work Simulator, however, is limited in that the maximum distance the hand-held bar can be moved is less than ten feet. This is a significant disadvantage because pushing and pulling on the job may often require pushing and pulling force to be exerted over a longer distance.
U.S. Pat. No. 4,451,037 discloses a three-wheeled mobile pushing exerciser which uses a brake drum and brake shoe to apply an isoinertial workload. As described by the inventor, this device is intended to be used as a tool to increase the power of an athlete during a pushing activity. A computer monitors performance and provides information regarding velocities and distance traveled.
A dynamic physiological function testing apparatus and method, described in U.S. Pat. No. 5,142,910, utilizes an electromagnetic brake assembly to apply resistance to a cart intended for use in assessing isoinertial pushing and pulling capacities. This invention incorporates computerized components to measure other physical parameters, including velocity, direction of movement and hand grip strength. There is no adjustability in the handle height on this device. Furthermore, the use of an electromagnetic brake and computerized monitoring of activity add unnecessary cost to the invention. This device is not commercially available.
U.S. Pat. No. 3,501,142 (issued May 1, 1970 to Johannson) reveals a bicycle exerciser with clinically varying resistance. This invention utilized an approach "wherein the brake wheel consists of a flywheel and the brake member of a brake strip engaging said flywheel, said pedal crank being in driving connection with a ratchet wheel which in turn is in driving connection with a cam wheel, said pedal crank thereby rotating said ratchet wheel and said cam wheel when pedaled, and an engagement between said cam wheel and said brake strip on a side thereof which is opposite to the flywheel, so that the rotation of the cam wheel brings about a varying tension of the brake strip and thus a variation of the brake effect."
The braking specific described by Johansson is now in the public domain. It also differs substantially from the present apparatus in five significant ways. First, the braking system on the present invention is mounted to a cart which moves across a surface, while the Johansson invention was specifically described as being mounted upon a stationary bicycle. Second, the present system utilizes a tension spring, as opposed to Johansson's adjustable cam to regulate the workload. Third, on the present device it is possible to affix a plurality of brakes, whereas on the Johannson creation it was possible to affix only one such brake to the bicycle. Fourth, the methodology used in connection with the present device is intended, in part, to assess consistency of effort during a dynamic pushing or pulling task, whereas the Johansson invention was intended for use as an exercise device. Fifth, the present invention is useful in simultaneously exercising the upper extremities, trunk and lower extremities, as opposed to exercising the lower extremities only (as occurs while using a stationary bicycle).
There are several methods and devices on the market which are used to assess pushing and pulling capacities in the clinical setting. My own invention uses a concealed tension spring braking system to provide a constant isoinertial resistance as is encountered in the "real world." The primary method of controlling the workload occurs through the clinician's manipulation of the braking apparatus. Utilizing the concept of "distraction testing," marked or unmarked weights can be added to the platform of the cart as a confounding variable for test subjects who are trying to control the outcome of the test. Adding or removing 100 pounds of weight will only marginally change the amount of force required to move the cart (fewer than approximately 10 pounds). By using multiple trials, with different amounts of weight on the cart available for visual inspection by the test subject, and clinician-controlled application of resistance on the device, it is possible to objectively assess consistency of effort during a dynamic pushing and pulling assessment. Furthermore, the invention will be useful in exercising a muscle during a physical conditioning program. All pushing and pulling assessment devices and protocols heretofore known suffer from a number of disadvantages:
a) Protocols relying on a therapist's visual observation of a subject to assess validity of effort depend on the accuracy of a subjective interpretation of performance and, thus, are prone to possible excessive inter-tester variability in interpreting test results. Testing protocols of this kind are vulnerable to legal challenge. Furthermore, if a test subject's abilities are miscalculated by the therapist, injury or misclassification of effort can result. PA1 b) Isometric devices measure a subject's capacity to generate pushing and pulling forces against an immovable object measure force which is not directly related to the ability to push or pull an object over a surface. PA1 c) Isometric testing measures physical capacity of a specific and limited arc in the range of motion of any joint. PA1 d) Isometric exercise benefits a specific and limited arc in the range of motion of any joint. PA1 e) There is no clear consensus on the usefulness of the coefficient of variation in analyzing consistency of effort during isometric testing. PA1 f) Isokinetic devices provide a descriptive account of the ability of a subject to push and pull an artificial workload that can be created only by devices in a clinical setting. However, there is no means by which an isokinetic performance can be used to predict the ability to push or pull the isoinertial workloads encountered in everyday life. PA1 g) No standardized method of assessing validity of performance on isokinetic equipment has been developed. PA1 h) In the evaluation of isoinertial pushing and pulling capacities, the BTE Work Simulator limits the distance over which pushing and pulling capacities can be tested. PA1 i) The objectivity of a pushing and pulling assessment can be affected if workloads on any device, including a sled or a cart, are available for visual inspection by the test subject. As a result of this limitation, the objectivity of an assessment can be tainted. PA1 j) Unless special adaptations are made to American Therapeutic's sled, that particular device can not be used in a gymnasium setting for training purposes because the runners of the sled may damage wooden floors. PA1 k) The computerized equipment described in U.S. Pat. No. 5,142,910, U.S. Pat. No. 4,451,037 and U.S. Pat. Nos. 4,337,050 and 4,473,226 and 4,475,408 are significantly more expensive than the present invention. Furthermore, such complicated devices require significant training time for operators of such equipment to become proficient their use. PA1 (a) to eliminate the subjective assessment of a clinician regarding the consistency of effort of a subject during a dynamic pushing and pulling assessment, replacing such assessment with a method and device which can be used to in a multiple trial protocol to objectively evaluate consistency of effort. PA1 (b) to provide a device which tests a subject's pushing and pulling capacities in an isoinertial mode, such as is encountered in everyday life. PA1 c) to provide a device which can test pushing and pulling capacities for a distance limited only by the floor space of a facility. PA1 d) to provide a device which is capable of offering the subject approximately 150 pounds of resistance, sufficiently high to cause a training effect in an athletic population and higher than most on-the-job requirements for pushing and pulling. PA1 (e) to provide a device which minimizes the visual cues that could affect the performance of a test subject. PA1 (f) to provide a training device which can be used on a gymnasium floor without damaging the surface of the floor. PA1 (g) to provide a device which is less costly and requires less training to become proficient in its use than computerized equipment.